Sahih Al Bukhari Hadith Number 1093

Narrated `Abdullah bin ‘Amir from his father who said: I saw the Prophet (peace be upon him) offering the prayer on his mount (Rahila) whatever direction it took.

18  Shortening the Prayers (At-Taqseer)
Hadith number 1093
Volume no 2
Chapter: 7 (To offer Nawafil on the back of animals)